var (
			reader io.Reader
			keyID  string
			key    []byte
			kmsCtx kms.Context
		)
		kind, _ := crypto.IsRequested(formValues)
		switch kind {
		case crypto.SSEC:
			key, err = ParseSSECustomerHeader(formValues)
			if err != nil {
				writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
				return
			}
		case crypto.S3KMS:
			keyID, kmsCtx, err = crypto.S3KMS.ParseHTTP(formValues)